The mechanism of action of the immunosuppressive effect of dCF is being determined in vitro with T and B lymphocyte cultures from mouse spleen and thymus. Measurements and adenosine metabolites, and DNA and RNA synthesis will be correlated with the suppression of blastogenesis by dCF resulting from the mitogenic response of the cells to concanavalin A and lipopolysaccharide. The metabolism of dCF and its incorporation into nucleic acids will also be assessed in ConA-stimulated spleen cells.